In Plain Sight's Martin Compston on becoming serial killer Peter Manuel: “It’s the darkest thing that I’ll ever play"

It’s ridiculous, but it’s true: Martin Compston’s superb performance as the often isolated, frequently luckless, mostly good-guy Steve Arnott, in Jed Mercurio’s Line of Duty, primes you to expect, at the very least, a serious, laconic guy in a sharp suit and a moral quandary.

Martin Compston as DS Steve Arnott in Line of Duty

Instead, he has quite a playful, expansive manner, although he’s thoughtful with it. He has an athletic energy; standing on Dean Street in London’s Soho, he looks like a young, Brando-era boxer, who doesn’t much like the violence but enjoys jumping around and wearing shiny shorts. I discover this is partly true because he started his career as a professional footballer.

To have had two dream careers before you hit 30 (he’s now 32) might cause a lesser person to be boastful, but he’s adamantly not.

“I was playing Scottish first division,” he explains. “That’s a bit different. I was lucky enough to have a glimpse of a dream for a year, so it was a big decision at the time – am I going to choose football or acting? But it wasn’t a choice between Manchester United and SpiderMan. It was a choice between one more year at Morton or being an unemployed actor.”

Line of Duty was the show that made him a face. “The scripts have always been phenomenal, and we started with a pretty solid cast, and were spoiled with all the people we’ve had as guest stars.

“But I didn’t expect it to be such a big hit with audiences, because we don’t make anything easy for them. And we always have these cliffhangers that leave people waiting, and that’s been dying out. With the box set, binge culture, everything’s so immediate.”

He lets that hang in the air for a quarter second then worries that maybe it sounds a bit po-faced.

“I’m guilty of it as well! It’s great, watching Netflix with a hangover. You can waste a day. But there is something to be said for community watching, going in to work the next day and talking about programmes you’re all watching together.”

He’s careful not to sound grand. “You’ve got to be aware of your limitations,” he says. “I’m 32 now. If I’d stayed in football, I’d be at the end of my career.”

He talks about his job as though it could be an in office but just happens to be a set; he loves the process not the trappings.

“Sure, you meet some amazing people, but I’ve got a lot of good people in my life. I genuinely love being on set. Apart from being with my wife or watching Celtic, that’s probably when I’m happiest.”

His career started in an unusual way – no childhood dreams segueing into drama school and on to TV via Casualty.

At 17, he was discovered from school by the director Ken Loach, who in 2000 cast him as Liam in Sweet Sixteen, a beautiful film about errant, anguished youth in Scotland. (It came out in 2002.)

He only went up for the part because he’d caught an earlier Loach movie by mistake: “Me and my friend took these two girls on a date. I can’t remember what we were meant to see, but it wasn’t on and we saw My Name Is Joe instead. Suddenly I saw characters I recognised, that spoke like me, and I thought, ‘I could be these people.’ That film ended in a big fight, with a bat. Me and my friend were running away to tell our other friends about it.”

It was a priceless apprenticeship, learning to act from Ken Loach. “You’re never really aware of cameras. It’s simple things – Ken never says ‘Action!’ It’s all really gentle and in your own time. He subtly manoeuvres you into your own story. He puts you in these situations and trusts you to make something out of it.”

The result was a hit at Cannes (winning best screenplay for Paul Laverty) and propelled Martin Compston into a new world, which came as a total surprise to him.

“I genuinely thought I’d make the film and that would be it.” It was only when he started getting roles afterwards that he realised this might be a bona fide career. “A lot of this is right time, right place. You can be the best in the world, but if nobody casts you, there’s nothing you can do.”

He spent three years in the BBC1 drama Monarch of the Glen, where he learnt the more pedestrian skills of TV acting. “That was like grammar school to me: work to your mark, think about camera angles.”

Now, via Line of Duty, he’s arrived at In Plain Sight, an ITV three-parter about some truly gruesome murders that happened in 1950s Lanarkshire. Compston leads the In Plain Sight cast as serial killer, Peter Manuel, in a cat-and-mouse scenario with Douglas Henshall’s detective, William Muncie.

It’s a role that has caused him, not self-doubt exactly, but a lot of questioning: “It’s hard to say these things, but on purely acting terms it’s an amazing part to play, the challenge of getting round it all. But you’ve got to remember that all his victims have families who loved them, who are still alive. It can’t all be him taunting the police, being brazen.

“One scene I thought was very important was Isabelle Cooke, just dancing. She’s the picture of life, the epitome of youth. These people shouldn’t just be defined as his victims. They were real people who had lives.”

In Plain Sight is shocking in its detail (“I think people will be struck by the severity of the crimes,” says Compston), yet it chooses psychological tension over blood and guts.

Muncie was dogged in his pursuit of Manuel, but the killer was equally obsessed with the detective. “He dropped birthday cards through his door, just to let him know he was close by. It was quite horrific, what this guy would do. It was my job to portray the madness without being too graphic.”

It’s not your classic period drama but, “they’ve done a magnificent job of recreating the time. It’s stylised. It’s beautiful.”

Compston and Douglas Henshall in ITV's In Plain Sight

The contrast between work and home couldn’t be starker: professionally, he’s spending his time trying to find some way to iterate the darkest, most repulsive parts of human nature.

“It’s the darkest thing that I’ve ever played and I’m sure ever will play. I was aware of who he was. He’s a sort of bogeyman in Scotland, but I was never aware of the depths of his depravity. He really was the embodiment of a psychopath – he had no empathy. By all accounts he could be charming. He was a great artist. But he was almost pantomime evil.”

Make sure to read the true story of Peter Manuel for more context behind the In Plain Sight story.

Some combination of art and life has wrought a change in the way Compston approached the role. “In days gone by, I’d have been locked in a darkened room for days. Normally, I’m an instinctive actor, I go with my gut. But I’m getting older, and this was more of a technical role for me. I didn’t feel emotionally connected to it. I definitely approached it differently.”

In real life, in June, he married the American actor Tianna Chanel Flynn, an event that produced some of the cutest wedding photos of all time.

“It’s been an interesting start to the marriage, no honeymoon and playing a serial killer. She’s a very patient woman. I’ve seen her for about four days since we got married. She’s very supportive and has family in Ireland as well. Hopefully, she’ll get over here before too long.”

Having acted for 15 years, he’s learnt a lot about how to do it without being changed for the worse. “In the past, I’ve got into this rut of staying in hotels and planes and being on your own and you just get too comfortable with it. You have to remember to be in the world.”

Line of Duty diehards will be relieved to hear that neither work nor play can divert him from playing Steve Arnott, who’ll be back in a fourth series, this time on BBC1.

“We’ve been doing this for nearly six years now. It’s good to be a character that you’ve made your own. You have to guard against complacency, but I know him inside out. I love slipping on that waistcoat and being Detective Arnott again.”

His love for the copper leaps off the screen; he laces the part with complexity and depth. His Lanarkshire villain can’t hope to capture the viewer’s heart, but will stalk their dreams.

Read more:

• Where was In Plain Sight filmed? All the Glasgow filming locations revealed

In Plain Sight is on ITV at 9pm tonight (7th June). Looking for something else to watch? Check out our TV Guide or for more news head to our Drama hub.